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Erythrasma
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
In its most typical form, erythrasma is characterized by well-defined, reddish-brown, flexural plaques that show fine scaling and no tendency to central clearing. It may also present with maceration of the toe webs.
The responsible organism, Corynebacterium minutissimum , is an inhabitant of normal human skin. Factors that predispose to clinically apparent infection include diabetes mellitus, obesity, human immunodeficiency virus (HIV), old age, and a humid environment.
Management Strategy
Erythrasma is often a trivial infection, but therapy may be requested because of the cosmetic appearance or because of pruritus. Coinfection with dermatophyte fungi or Candida albicans is common and may influence the choice of treatment.
Fusidic acid cream is the topical treatment of choice where no concomitant yeast or fungal infection is found. It is both effective and well tolerated. Despite the apparent efficacy of fusidic acid cream alone, a combination of oral and topical treatment for extensive or stubborn toe web infections might be more effective.
Topical imidazoles (miconazole, clotrimazole) are well tolerated and also effective against concomitant fungal or yeast infection.
There has been recent evidence for topical mupirocin 2% ointment as a treatment. However, more studies and comparison to placebo is required to evaluate its efficacy.
When the disease is extensive or when compliance with topical therapy is unlikely, oral antibiotics such as single-dose clarithromycin or oral erythromycin should be considered.
A combination of oral and topical treatment may be required for stubborn infections, particularly of the toe webs.
Specific Investigations
Rapid confirmation of the diagnosis is achieved by examination of the skin under Wood (long-wave ultraviolet) light. The characteristic coral-red fluorescence observed is due to the production of coproporphyrin III by the organism. Fluorescence may not be seen if the patient has bathed immediately before examination. Culture is unreliable because the organism does not always grow satisfactorily. Microscopy of skin scrapings is performed to seek evidence of concomitant infection, such as the presence of fungal hyphae or yeasts.
First-Line Therapies
A comparison between the effectiveness of erythromycin, single dose clarithromycin and topical fusidic acid in the treatment of erythrasma
Avci O, Tanyildizi T, Kusku E. J Dermatolog Treatment 2013; 24: 70–4.
Of the 151 patients included in this study, around two-thirds had toe web infections. A complete response (defined as no fluorescence) was observed in 30/31 patients treated with 2% fusidic acid cream twice daily for 14 days in this double-blind, placebo-controlled trial. The response was superior to oral clarithromycin (20/30), oral erythromycin (16/30), placebo cream (4/30), and placebo tablets (1/30). The authors acknowledged the limitations of the grading system of fluorescence used to assess response. They mention that the higher efficacy of fusidic acid cream over oral antibiotics might well be due to the removal of coproporphyrin III from the stratum corneum during topical applications.
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